A so-called “dark money” group is coming to Democrat Kay Hagan’s aid in North Carolina, unleashing a new TV ad Wednesday that attacks Republican frontrunner Thom Tillis. (See ad below.)

Patriot Majority USA, a nonprofit that doesn’t disclose its donors, is putting $500,000 toward running the ad for the next eight days, a spokesman said.

The 30-second spot doesn’t mention Hagan but it appears to be a response to ads from Americans for Prosperity attacking the first-term senator for supporting the federal health care law. AFP – which is backed by the brothers Charles and David Koch brothers – has spent more than $6.5 million, on its effort with some estimates putting the price tag at $8 million-plus.

In the “Bad Company” ad, Patriot Majority fights back on the same turf: the health care law. It attacks Tillis for opposing the Affordable Care Act, saying his stance means he “sides with health insurance companies.” The ad also claims Tillis “supports a plan that would end Medicare as we know it” for backing U.S. Rep. Paul Ryan’s proposed budget. A version of the claim was dubbed by fact-checker PolitiFact as the 2011 “lie of the year.”

The kicker – “Thom Tillis, he’s with special interests, hurting North Carolina families” – reiterates a theme Democrats are trying to use against Tillis. It also is the theme GOP rival Greg Brannon is using against the House speaker, who also faces Charlotte pastor Mark Harris and two other lesser-known candidates in the primary race.

Tillis campaign spokesman Jordan Shaw called on Hagan to speak out. “While Kay Hagan denounces the use of outside funds against her, liberals in DC are spending hundreds of thousands of dollars falsely attacking Thom Tillis,” he said in a statement. “Where is Kay Hagan’s statement condemning these ads? Liberals in DC know that Thom Tillis is the candidate to beat Kay Hagan, so they’re trying to use the same tired scare tactics to save Hagan’s rubber stamp for the Obama agenda.”

Hagan criticized Americans for Prosperity for not disclosing its donors and bashed the special interest money behind the effort. Now she is getting help from the same type of group.

Hagan campaign spokeswoman Sadie Weiner on Wednesday said the senator supports the DISCLOSE Act to make all groups disclose donors and “increase transparency and accountability for all outside groups – Democratic or Republican.”

But Weiner stopped short of criticizing Patriot Majority for running the ads.

A Patriot Majority USA spokesman did not say where in the state the ad would appear but the size of the ad buy means it won’t reach the same voter-awareness levels as the AFP ads. If video is not working below, see ad here.

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